Okay, being in love with the game, I'm gonna have myself a little rant:
By means of gameplay it's in no ways revolutionary(no pun intended). It's a solid stealth game, but unfortunately if you play it guns blazing, it loses a lot of its inherent complexity and pacing. But what makes is absolutely amazing in my book is that it's the showcase point of "games can be art". The plot itself is much deeper than advertised if you're ready to actually embrace the very real dilemma it presents - in the age where machine is more efficient than man, at which point does a human end, and a machine begins? If my whole body is augmented, changed, upgraded mechanically, what does that make me? A robot? Something dead? Or is the very feeling of belonging to the human race, the feeling of identity make me human as long as I acknowledge it? This game's plot does a great job of presenting an actual, very real issue that becomes extremely intricate if you just find some time to think about it.
Moral dilemmas aside, this game is full of depth you can't even begin to scratch without extreme attention, which makes the content so rich and fulfilling. I cringe when someone says that the world of, say, Skyrim, is extraordinary because it's so big and full of stuff to do. Because it isn't. The hubs of DE:HR aren't very big, but they merge seamlessly into actual gameplay and are so detailed and vivid that you WANT to explore just to spot some things that let you put together the big picture.
The best example of this is Jensen's apartment, in which i spent around an hour wallowing in the sheer multitude of details that went into it. On the table, there's alcohol, a single glass, a rifle lying right next to the sofa. So Jensen is not only in chronic depression, he's also paranoid as fuck. Next, I look around the pictures, showing Adam and Megan, the remnants of his baseball career, military buddies etc. But then I see something that puts me in an entirely different perspective regarding Jensen - in the corner of the apartment, there's a tiny little table with clockwork equipment scattered around. And next I see a post-it note on the window, which reads: "The quick brown fox jumped over the lazy dog" scribbled terribly. And that brings me to the point which makes me regard the game as ingenious. Because nobody tells you what Jensen had to get through after his limbs were replaced. Before he was the awesome aug-superman. "The quick brown fox jumped over the lazy dog" is a phrase that contains all letters from the english alphabet. Jensen was teaching himself to write and control pressure in his hands by writing kiddy sentences and doing clockwork, all while grief over his fiancee that he couldn't save was eating away at him, and he wasn't even sure if he could call himself a human being anymore.
If you take your time to appreciate things like these in video games, no, in all of art, you might grow up to recognize that there are works of fiction that are good and expansive (say, Mass Effect) and there are pieces of art that are something more.
I'm not even presenting the best visual design in video game history, something more on par with Blade Runner than any sci-fi movie of the last decade, and maybe, just maybe, I made you look at video games like more than just things you play. Like something you experience, and something that immerses you.